typedef struct dulnode
{
	ElemType data;
	struct dulnode *prior,*next;
}DulNode;

/*
	p为插入前驱
	s = (DulNode *)malloc(sizeof(DulNode));
	s -> next = p -> next;
	p -> next -> prior = s 
	s -> prior = p;
	p -> next = s; 



	删除p
	p ->next -> prior = p -> prior;
	p ->prior -> next = p -> next;
	free(p);
*/